β-defensin expression in different regions (caput, corpus and cauda) of the human epididymis. (A) Heatmap showing β-defensin levels in RNA-seq data from human epididymis tissues (Log scale; 2 donors) (Browne, et al., 2016). Epididymis positive control markers: CLU= clusterin; CRISP1= cysteine rich secretory protein 1. (B) Expression levels of 6 β-defensins (DEFB1, DEFB104, DEFB108, DEFB121, DEFB131 and DEFB4) assayed by RT-qPCR relative to −2 microglobulin in epididymis tissue and sperm isolated from 3 different donors (i-iii) (none of the donors overlap with those shown in panel A).